We can’t direct the wind, but we can adjust the sails: using models to predict hypoxia in Lake Erie

We can’t direct the wind, but we can adjust the sails

Using models to predict hypoxia in Lake Erie

BY MICHAEL LIM

Rising temperatures and agricultural run-off are leading to harmful reductions in oxygen levels in the waters of Lake Erie, but Integrative Biology Professor Josef Ackerman is finding new ways to predict when these damaging events can occur.

Low levels of dissolved oxygen – a phenomenon known as hypoxia – can reduce the growth of aquatic organisms or cause them to migrate to other waters. If levels are low enough, it may become fatal.

Ackerman has a deep interest in bottom-dwelling aquatic organisms and has been studying lake dynamics for nearly 30 years.

“My first foray into working with Lake Erie was in the mid-90s,” say Ackerman. “At the time, we were focused on zebra mussels, but then we came across the broader issue of hypoxia.”

Lake Erie may be the smallest of the Great Lakes by volume, but it is the most biologically productive. This is due partly to nutrient runoff from farms, which leads to algal blooms. When the algae die, they settle on the bottom of the lake and decompose, consuming oxygen in the process. This creates a hypoxic layer of water at the bottom of the lake. But because Lake Erie is large and relatively shallow, strong winds can cause upwelling that brings hypoxic water nearer to the surface.

These hypoxic episodes directly affect not only aquatic species in the affected areas, but humans as well, reducing the quality and taste of drinking water taken from the lake.

Interestingly, it wasn’t until Ackerman and post-doc Dr. Aidin Jabbari attended a regional conference that they became aware that Lake Erie hypoxia via upwelling was a shared interest across disciplines, attracting physicists and mathematicians as well as biologists. A modelling expert from National Oceanic and Atmospheric Administration (NOAA), Dr. Mark invited Ackerman and Jabbari to join their team.

“All people, not just researchers, tend to think in isolation,” says Ackerman. “So when you’re inspired to learn about something, and then find out there are several like-minded groups out there all searching and trying to understand the same thing… it is really kind of cool.”

The team used several years of meteorological data to develop a computational model that could predict future hypoxic events based on environmental conditions. They then tested their model against a set of sensors placed throughout the lake.

The model and field data revealed that temperature and wind direction are critical in creating hypoxic conditions. In particular, hypoxia is strongest during the summer months, and strong winds can trigger earlier periods of hypoxia on their respective shores. For example, a southwesterly wind results in earlier hypoxia on the southern shores of Lake Erie, while north-easterly winds reverse the pattern.

The model’s accuracy hints at the unexpectedly large role that environmental conditions may play in hypoxia patterns in Lake Erie.

While little can be done to alter the weather, it is helpful to know when and where hypoxia is likely to occur. For example, drinking water treatment plants need to know when to reduce water intake, while biologists need to know which areas to avoid sampling from when trying to estimate aquatic populations.

“We’ve learned a lot from studying Lake Erie, and hope that people will learn and build upon what we’ve learned,” says Ackerman. “Only by understanding how all the different processes involved work and affect each other, can you then know how to bring positive change.”

Read the full study in the Journal of Geophysical Research: Oceans.